Centerfire Cartridge Primer Safety Shield

ABSTRACT

A centerfire cartridge with improved ballistic characteristics for use in lever action firearms having tubular magazines is shown. A primer safety shield allows a sharper pointed bullet to be used without increased danger of inadvertent firing when a cartridge is placed in nose to base contact in a magazine.

FIELD OF INVENTION

This invention relates to firearms ammunition and more particularly torifle and pistol centerfire cartridges for use in magazines where thecartridge primer may come in contact with the tip of adjacentcartridges.

BACKGROUND OF INVENTION

The background of the firearms ammunition industry problems andchallenges addressed in part by the present invention is set forth ingreat detail in the specification of U.S. Pat. No. 7,380,502 and iscopied in part herein.

Many popular types of rifles such as lever action rifles employ tubularmagazines in which a single line of cartridges is stored in acylindrical tube below the rifle barrel. The cartridges are arrangednose first with a compressed spring and piston forward of the nose ofthe forward most cartridge. The spring pressure transmits through therow of cartridges and forces the rear most cartridge into the actionwhen the action is cycled. Centerfire cartridges have primers centeredin the base of the cartridge and it is essential to ensure that the noseof one bullet does not act as a firing pin and strike the primer of thenext cartridge. Traditionally this has required the use of blunt nosedbullets having diameters greater than the diameter of the centerfireprimer to ensure any force transmitted to the primer is distributed overa large enough area to ensure that primer discharge will not occur.

Unfortunately flat or blunt nose bullets are aerodynamically inefficientcompared to pointed bullets used in other types of rifles. This meansthat they lose more velocity as a function of distance traveled than asharp pointed bullet resulting in less energy downrange and increasederrors requiring shooter adjustment. A ballistic coefficient (BC) of0.200 depending on caliber and weight of the bullet is common for bluntnosed bullets while BC values of 0.250 to 0.350 are achieved withcomparable sharp nosed bullets. Translated into hunting values a leveraction rifle is considered effective to about 100-150 yards while spirepoint bullets of comparable weight and muzzle velocities are effectivebeyond 250 yards.

SUMMARY OF PRESENT INVENTION

The present invention overcomes the flat nose bullet limitations oftubular type magazines such as the lever action rifle tubular magazinesdescribed in the referenced patent by providing a centerfire firearmcartridge with a safety shield about the primer such that the bulletfixed in such a cartridge may be more pointed than the traditional bluntnose bullets and substantially achieve the greater ballisticcoefficients of more sharply pointed cartridges such as shown in thereferenced US patent. By shielding the primer with a safety shieldhaving a small central hole just large enough to admit a firing pinblunt nose bullets are no longer required to prevent unintendeddischarge of the primer and cartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of cartridges in a tubular magazineaccording to the present invention.

FIG. 2 is a sectional view of three cartridges with A showing a priorart cartridge, B showing a modified case with large rifle primer andsafety shield; and C showing a standard case with small primer andsafety shield. according to the present invention;

FIG. 3 is a sectional view of a small primer A, safety shield B, andassembly C;

FIG. 4 is a view similar to FIG. 3 with a large primer A, safety shieldB, and assembly C;

FIG. 5 is a sectional view of a cartridge case showing anotherembodiment of my invention;

FIG. 6 is a view similar to FIG. 5 showing a still further embodiment ofmy invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to FIG. 2 cartridge A is a cross section of a conventionalcenter fire cartridge body 10 standardized one hundred years or so ago.Millions and millions of this type of cartridge body have been made andmany are still available for reloading with a new large primer 12,powder and bullet of choice. Regardless of the caliber of the cartridgethe diameter of the large primer has stayed at 0.212 inches and it hasbeen made of cartridge brass that may be easily indented to compress theprimer mixture against an anvil to fire the cartridge.

Cartridge B of FIG. 2 is a cross section of a first embodiment of myinvention where a large primer 12 has been press fitted into a safetyshield 14. Shield 14 is cup shaped and has a center hole 16 in the base.Hole 16 must be large enough to admit the firing pin but small enough toexclude the more pointed tip of the bullet to be used in the cartridge.A range of 0.060-0.110 inches, depending on the diameter of the bullettip, seems to be satisfactory. In a preferred embodiment a diameter of0.100 inches has been found to be suitable. A typical shield 14 mighthave an outside diameter of 0.266 inches. Shield 14 is preferably madeof nickel plated steel with a thickness sufficient to prevent firing ofthe primer by recoil or other shock. The assembled shield 14 and primer12 are press fitted into an appropriately enlarged cavity in the base ofthe cartridge 10′. While this would require modification of existingcartridge bodies and changing of the primer cavity dimensions in newmanufacture the existing large primers could still be used.

Cartridge C of FIG. 2 shows a variation of my invention in which thelarge primer cavity diameter of 0.212 inches is maintained in thecartridge body 10″ and a smaller safety shield 18 is used to protect a“small” primer 20 which usually has an outside diameter of 0.175 inches.Again shield 18 has a center hole 22 with a diameter of 0.100 inches aninside diameter of 0.175 inches and an outside diameter of 0.212 inches.These dimensions allow the primer 20 to be press fitted into the shield18 and the assembly press fitted into the large primer cavity in thestandard cartridge body. Shield 18 is preferably made of nickel platedsteel with sufficient strength so the thinner wall will still protectthe primer from firing. It may be seen that in cartridge C the height ofsmall primer 20 may be shorter than standard since safety shield 18 issized to just fit in the large primer cavity in standard cartridges.

As shown in FIG. 1 the foregoing safety shields 14 and 18 preventpointed bullet nose 24 from contacting the primer of the bullet in frontof it. Obviously the bullets will not always be in perfect alignment asshown in FIG. 1 but when skewed there is even less possibility ofcontact with the primer.

Referring now to FIG. 3 a small primer cup 26 is shown with safetyshield 28 sized to receive cup 26 in a press fit and the completeassembly staying within the outside diameter of 0.212 inches to allowpress fitting in the standard cartridge body primer cavity. With thisconfiguration of my invention the millions of existing cartridge shellscan be reloaded using standard readily available parts and tools. Alsonew cartridges made with this safety shield may be used in lever actionrifles with tubular magazines without sacrificing any appreciableaccuracy or range with safety equal to or better than blunt nosebullets.

Referring now to FIG. 4 a primer safety shield for the large primer withits 0.212 inch outside diameter and 0.118 inch depth. Here typically thesafety shield would have an outside diameter of 0.266 inches and anoverall depth of 0.145 inches. While this would require resizing theprimer cavity in the standard cartridge, for some applications it may bepreferable to the configuration of FIG. 3.

FIG. 5 shows another embodiment of the invention in which the safetyshield takes the form of a nickel plated steel flat washer 30 with acenter hole of 0.100 inches press fitted into the base of the cartridgebelow the primer 32. This configuration gives the same protection andperformance advantages as the foregoing alternatives although requiringsome additional modification to the standard cartridge cases.

FIG. 6 shows a still further embodiment in which a nickel plated washer34 having a central hole of 0.100 inches diameter and an outer diametermatching the primer 36 used in the primer cavity of the cartridge. It isaffixed to the primer 36 before press fitting the assembly into thecartridge body. Safety shield washer 34 may be epoxyed, welded orotherwise affixed to the primer bottom.

While there are given above certain specific examples of this inventionand it application in practical use, it should be understood that theyare not intended to be exhaustive or to be limiting of the invention. Onthe contrary these illustrations and explanations herein are given inorder to acquaint others skilled in the art with this invention and theprinciples thereof and a suitable manner of its application in practicaluse.

1. A firearm cartridge comprising: an elongated cylindrical casedefining an interior volume containing gunpowder having a rear endincluding a central primer pocket receiving a primer and a primer safetyshield member and a forward end opposite from the rear end of the casefor receiving therein a bullet; said primer safety shield member beingformed about at least the exterior surface of said primer and having acentral hole in the surface thereof; said primer safety shield having adiameter less than the diameter of said elongated cylindrical case andsubstantially greater than the diameter of a firing pin of a firearm; abullet received in said forward end of said elongated cylindrical case;said bullet having a rigid tapered forward nose portion with a diameterless than said primer safety shield member diameter; and said safetyshield member central hole having a diameter less than the diameter ofsaid tip of said bullet tapered forward nose portion.
 2. The firearmcartridge of claim 1 wherein said safety shield member is cup shaped andsaid central hole has a diameter between 0.060 and 0.110 inches.
 3. Thefirearm cartridge of claim 2 wherein said safety shield member centralhole has a maximum diameter of 0.100 inches.
 4. The firearm cartridge ofclaim 3 wherein said bullet tapered nose portion has a diameter of atleast 0.110 inches.
 5. The firearm cartridge of claim 1 wherein saidprimer safety shield member comprises an outer nickel plated steel cupmember press fitted about said primer and inserted in the base of saidelongated cylindrical case.
 6. The firearm cartridge of claim 1 whereinsaid safety shield member comprises a steel cup press fitted about saidprimer having a central hole in the base thereof with a diameter of lessthan 0.101 inches and a thickness sufficient to support the impact of acolumn of firearm cartridges in a tubular rifle magazine withoutdetonation of the primer in said safety shield member when the rifle isdropped butt first from a height of at least fifteen feet.
 7. Thefirearm cartridge of claim 1 wherein said safety shield member comprisesa steel cup press fitted about said primer having a central hole in thebase thereof with a diameter of less than 0.101 inches and a thicknesssufficient to support the impact of a column of firearm cartridges in atubular rifle magazine without detonation of the primer in said safetyshield member under heavy recoil.
 8. The firearm cartridge of claim 1wherein said safety shield member is a washer having a central hole ofless than 0.101 inches secured in the bottom surface of said elongatedcylindrical case; and said washer having a thickness sufficient towithstand rifle impacts as set forth in claims 6 and
 7. 9. The firearmcartridge of claim 1 wherein said safety shield member is a washerhaving a central hole of less than 0.101 inches secured to the bottomsurface of said primer; and said washer having a thickness sufficient towithstand rifle impacts as set forth in claims 6 and
 7. 10. A firearmcartridge comprising: an elongated cylindrical case defining an interiorvolume containing gunpowder having a rear end including a central primerpocket receiving a primer and a primer safety shield member and aforward end opposite from the rear end of the case for receiving thereina bullet; said primer safety shield member being formed cup like aboutthe exterior surface of said primer and having a central hole in thebottom thereof; said primer safety shield having a diameter less thanthe diameter of said elongated cylindrical case and substantiallygreater than the diameter of a firing pin of a firearm; a bulletreceived in said forward end of said elongated cylindrical case; saidbullet having a rigid tapered forward nose portion with a ballisticcoefficient of greater than 0.250; and said safety shield member centralhole having a diameter less than the diameter of the tip of said bullettapered nose portion.
 11. A firearm cartridge component comprising; acylindrical cup body open at the top; said body bottom having a centralhole; said central hole having a diameter less than the tip diameter ofthe projectile to be used in the firearm cartridge.
 12. A firearmcartridge component as claimed in claim 11 wherein said cup body has anouter diameter equal to the large primer diameter and an inner diameterequal to the outer diameter of a small primer.
 13. A firearm cartridgecomponent as claimed in claim 11 wherein said body has an inner diameterequal to the outer diameter of a large primer and an outer diameter lessthan the cartridge body diameter.
 14. A firearm cartridge componentcomprising: a cylindrical flat body portion; said body portion having acentral hole; said central hole having a diameter less than the tipdiameter of the projectile to be used in the firearm cartridge.
 15. Afirearm cartridge component as claimed in claim 14 wherein said flatbody portion has an outer diameter equal to the primer diameter.
 16. Afirearm cartridge component as claimed in claim 14 wherein said flatcylindrical body portion has an outer diameter greater than the primerdiameter.